fix: pin nested letta resolution in dev subagent shells (#937)

src/tests/tools/shell-env.test.ts

@@ -0,0 +1,123 @@
+import { describe, expect, test } from "bun:test";
+import { spawnSync } from "node:child_process";
+import * as path from "node:path";
+import {
+  ensureLettaShimDir,
+  getShellEnv,
+  resolveLettaInvocation,
+} from "../../tools/impl/shellEnv";
+
+describe("shellEnv letta shim", () => {
+  test("resolveLettaInvocation prefers explicit launcher env", () => {
+    const invocation = resolveLettaInvocation(
+      {
+        LETTA_CODE_BIN: "/tmp/custom-letta",
+        LETTA_CODE_BIN_ARGS_JSON: JSON.stringify(["/tmp/entry.ts"]),
+      },
+      ["bun", "/something/else.ts"],
+      "/opt/homebrew/bin/bun",
+    );
+
+    expect(invocation).toEqual({
+      command: "/tmp/custom-letta",
+      args: ["/tmp/entry.ts"],
+    });
+  });
+
+  test("resolveLettaInvocation infers dev entrypoint launcher", () => {
+    const invocation = resolveLettaInvocation(
+      {},
+      ["bun", "/Users/example/dev/letta-code-prod/src/index.ts"],
+      "/opt/homebrew/bin/bun",
+    );
+
+    expect(invocation).toEqual({
+      command: "/opt/homebrew/bin/bun",
+      args: ["/Users/example/dev/letta-code-prod/src/index.ts"],
+    });
+  });
+
+  test("resolveLettaInvocation returns null for unrelated argv scripts", () => {
+    const invocation = resolveLettaInvocation(
+      {},
+      ["bun", "/Users/example/dev/another-project/scripts/run.ts"],
+      "/opt/homebrew/bin/bun",
+    );
+
+    expect(invocation).toBeNull();
+  });
+
+  test("resolveLettaInvocation does not infer production letta.js entrypoint", () => {
+    const invocation = resolveLettaInvocation(
+      {},
+      [
+        "/usr/local/bin/node",
+        "/usr/local/lib/node_modules/@letta-ai/letta-code/letta.js",
+      ],
+      "/usr/local/bin/node",
+    );
+
+    expect(invocation).toBeNull();
+  });
+
+  test("letta shim resolves first on PATH for subprocess shells", () => {
+    if (process.platform === "win32") {
+      return;
+    }
+
+    const shimDir = ensureLettaShimDir({
+      command: "/bin/echo",
+      args: ["shimmed-letta"],
+    });
+    expect(shimDir).toBeTruthy();
+
+    const env = {
+      ...process.env,
+      PATH: `${shimDir}${path.delimiter}${process.env.PATH || ""}`,
+    };
+    const whichResult = spawnSync("which", ["letta"], {
+      env,
+      encoding: "utf8",
+    });
+    expect(whichResult.status).toBe(0);
+    expect(whichResult.stdout.trim()).toBe(
+      path.join(shimDir as string, "letta"),
+    );
+
+    const versionResult = spawnSync("letta", ["--version"], {
+      env,
+      encoding: "utf8",
+    });
+    expect(versionResult.status).toBe(0);
+    expect(versionResult.stdout.trim()).toBe("shimmed-letta --version");
+  });
+
+  test("getShellEnv sets launcher metadata when explicit launcher env is provided", () => {
+    const originalBin = process.env.LETTA_CODE_BIN;
+    const originalArgs = process.env.LETTA_CODE_BIN_ARGS_JSON;
+
+    process.env.LETTA_CODE_BIN = "/tmp/explicit-bin";
+    process.env.LETTA_CODE_BIN_ARGS_JSON = JSON.stringify([
+      "/tmp/entrypoint.js",
+    ]);
+
+    try {
+      const env = getShellEnv();
+      expect(env.LETTA_CODE_BIN).toBe("/tmp/explicit-bin");
+      expect(env.LETTA_CODE_BIN_ARGS_JSON).toBe(
+        JSON.stringify(["/tmp/entrypoint.js"]),
+      );
+    } finally {
+      if (originalBin === undefined) {
+        delete process.env.LETTA_CODE_BIN;
+      } else {
+        process.env.LETTA_CODE_BIN = originalBin;
+      }
+      if (originalArgs === undefined) {
+        delete process.env.LETTA_CODE_BIN_ARGS_JSON;
+      } else {
+        process.env.LETTA_CODE_BIN_ARGS_JSON = originalArgs;
+      }
+    }
+  });
+});